This application is based on and incorporates herein by reference Japanese Patent Applications No. 2000-6637 filed Jan. 14, 2000 and No. 2000-362967 filed Nov. 29, 2000.
1. Field of the Invention
The present invention relates to a self-diagnosis of a vehicle control computer system.
2. Related Art
In a vehicle control computer apparatus, if abnormality detection for the respective system parts such as sensors and actuators cannot be properly made, an undesired trouble might occur in running, and at worst, the running might be disabled. For this reason, the computer apparatus using CISC-type microcomputer, for instance, is provided with a self-diagnosis function for improvement in reliability. That is, operating statuses of a computer part, sensors and the like are automatically checked at appropriate intervals. When an abnormality is detected continuously, a warning light is turned on to notify a user of the abnormality, and/or an abnormality code to notify a repair person of the content of the abnormality is outputted, thus realizing a diagnosis function.
Since the result of abnormality detection (determination status) is stored as 1-bit flag information in a normal RAM (volatile memory), a battery backup RAM (nonvolatile memory), EEPROM (nonvolatile memory) or the like, a large storage area is necessitated for one diagnostic item. In case of diagnostic processing for about 200 diagnostic items, the total storage area for the determination status is not negligible.
Further, in recent years, a RISC-type microcomputer, having an increased computation speed, with use of reduced number of commands, is mainly used. In the RISC microcomputer, byte-unit operation commands are used, whereas bit operation commands tend to decrease. If there is no bit operation command, it is necessary to combine plural commands, which reduces the computation operation speed.
In order to solve this problem, byte-unit data operation executable by 1 command is made. For example, if the most significant bit is set in 1 byte area, xe2x80x9c128xe2x80x9d (10000000 in binary representation) is stored. That is, as no bit operation command is used in the RISC microcomputer, to avoid reduction of computation speed, it is necessary to ensure a storage area in 1 byte units. As a result, the storage area is wastefully used.
In a conventional method of storing the diagnosis result as flag information, since a processing program on the basis of bit operation is designed in the RISC microcomputer in which no bit operation command is used. The designing is disadvantageous from the point of the number of designing steps. In some cases, actually bit-unit operations are made, and in such cases, the computation speed is lowered.
The present invention has its object to reduce a storage area necessary for diagnosis and to reduce the number of designing steps of processing program, while enabling information processing operation in a RISC-type microcomputer.
According to the present invention, a vehicle control apparatus having a diagnosis function stores diagnosis determination status of different levels as numerical values set in correspondence with each determination status while avoiding mutual numerical overlap among the different levels. Preferably, the numerical value is within a range of 0 to 255 which can be defined by a single byte.
The apparatus executes a determination status transition processing to change the stored determination status of a previous trip period to a new determination state when the determination status changes between successive trip periods. In this instance, the numerical value is set within a numerical range which is exclusive to each level of the diagnosis statuses. The apparatus increases or decreases the numerical value to attain the transition processing.